1. Field of the Invention
The invention relates to a method of combustion for a liquid fuel and also to a burner for the application of said method. It relates more particularly to a self-cleaning complete combustion burner head.
2. Description of the Prior Art
According to a well-known burner principle, liquid fuel is atomized by means of a sprayer, then mixed with air in a combustion head, before burning it in a yellowish flame. A system based on this technique necessitates, for good combustion, the production of the flame in a sufficiently voluminous space, so that all the atomized fuel particles have time to be consumed. In fact, if the hearth wherein this form of combustion occurs is too small, the unconsumed liquid particles are projected on to the walls which, at too low a temperature, cause condensations and a certain pollution (soot, tar, etc.). It results therefrom that the combustion yield as well as the coefficient of thermal exchange of the exchanger decrease through the insulation occasioned by the soot film which is interposed between the flame and the wall of the hearth. Moreover, the minimum flow rate of the sprayers is limited.
It is an object of the invention to reduce the volume of combustion gases thus enabling reduction of the dimensions of the exchanger of heating equipment, and in particular of the hearth. In fact, combustion in the presence of a blue flame, at very high temperature, as is caused by the apparatus described in the present invention, enables a reduction of the combustion chamber by at least 90%, and consequently reduction of weight and hence of cost price of equipment to a great extent.
Reduction in the volume of exchangers enables decrease in the normal dimensions of domestic or industrial boilers, which results in considerable financial gain, the heating equipment or the location in which the equipment is situated being of reduced size.
According to another known burner principle, the liquid fuel is gasified, for example in a pot, and then burnt, mixed with air, in the form of yellow flame, sometimes blue, according to the method adopted. This form of combustion has the drawback of being difficult to control, according to the draft of the chimney, and generally necessitates an excess of air, which reduces the yield.
In another known principle of burner, the combustion is carried out according to both said types of burner; thus, at the start, the combustion is done in atomized form of the liquid fuel, by spraying, by means of a cup or rotary bell, the fuel then being gasified by heating said bell or cup. Generally combustion by a blue flame results. Devices based on this principle have numerous drawbacks, due principally to the equilibrium and wear of the moving parts and their fouling.
It is another object of the invention to enable complete combustion of liquid fuel, whatever the power desired, very low (less than 1 liter per hour) or very high (several tens of liters per hour), without the presence of spraying members, such as a spray head or rotary cup. In addition, such combustion, in the form, for example, of a completely blue flame, according to the type of fuel used, avoids any atmospheric pollution.
Combustion of a liquid fuel, such as is produced in conventional systems, takes place according to a process in the course of which the conversion for liquid state to gaseous state, more or less well-mixed with combustion air, is carried out in the middle of the flame. In fact, a customary burner spray head does not permit intimate pre-mixing of air and gasified fuel, since the gasification is effected by explosion of micro-drops of atomized liquid fuel, which explosion is caused by the temperature which exists in the flame. Thus the flame is yellow and very animated.
It has also been conceived to draw liquid fuel by the combustion supporting air itself, so as to obtain at the same time, vaporization of said fuel and mixing of the latter with the combustion supporter. This method of procedure has drawbacks, due notably to the absence of pre-mixing the vaporized fuel and the combustion supporting air. The inventor has in fact observed, that to obtain good combustion, it was necessary to respect certain conditions and to establish a cycle in three phases.